Prosthetic foot

ABSTRACT

A prosthesis is disclosed for improving the gait and comfort qualities of the amputee that participates in walking, running and jumping activities. A foot and an ankle of the prosthesis are monolithically formed as a resilient member including a strut which forms an ankle joint. A hole extends through the resilient member with the periphery of the hole forming an anterior side surface of the strut. The resilient member anterior to the hole includes a gap to permit motion about the ankle joint axis while providing a stop in dorsiflexion. The hole is elongated upwardly such that the strut is upstanding and anterior convexly curved.

RELATED APPLICATIONS

[0001] This application is a continuation-in-part of application Ser.No. 10/790,177, filed Mar. 2, 2004, which is a continuation ofapplication Ser. No. 09/917,660, filed Jul. 31, 2001, now U.S. Pat. No.6,743,260, issued Jun. 1, 2004, which is a continuation-in-part ofapplication Ser. No. 09/742,077, filed Dec. 22, 2000, now U.S. Pat. No.6,443,995, issued Sep. 3, 2002. This application is also acontinuation-in-part of application Ser. Nos. ______ and ______, eachfiled Apr. 1, 2004, which are each:

[0002] a continuation-in-part of application Ser. No. 10/473,682, whichis the U.S. national designated filing under 35 U.S.C. §371 ofinternational application PCT/US02/09589 filed Mar. 29, 2002, which is acontinuation-in-part of U.S. application Ser. No. 09/820,895, filed Mar.30, 2001, now U.S. Pat. No. 6,562,075 issued May 13, 2003; and

[0003] a continuation-in-part of application Ser. No. 10/263,795 filedOct. 4, 2002, which is a continuation of application Ser. No.09/820,895, filed Mar. 30, 2001, now U.S. Pat. No. 6,562,075 issued May13, 2003. The disclosures of these related applications are herebyincorporated by reference.

TECHNICAL FIELD

[0004] A prosthetic foot that mimics the human foot in function isdisclosed. The prosthetic foot has hindfoot triplanar motion capability,biplanar midfoot and forefoot motion capabilities and high low dynamicresponse characteristics for improving gait and comfort qualities of theamputee in walking, running and jumping activities. An ankle pyloncomponent providing hindfoot triplanar motion capability for upgradingan existing low profile prosthetic foot is also disclosed.

BACKGROUND AND SUMMARY

[0005] Those in the field of prosthetics have in the past manufacturedprosthetic feet which permit varying degrees of motion capability. Mostof the known prosthetic feet utilize metal hinges with rubber bumpers toenable this motion capability. These components are sources formechanical failures and wear. The known prosthetic feet are alsogenerally expensive to produce and maintain. None of the conventionalprosthetic feet mimic human gait characteristics, e.g., while knowndesigns allow some motion capability, the conventional prosthetic feetdo not reflect humanoid characteristics. These characteristics relate tothe biomechanical function of the human foot and ankle joint in gait.The prior art prosthetic feet have not achieved true human gaitcharacteristics because their design features do not mimic the humanfoot.

[0006] The human foot is a complex comprised of twenty-six separatebones. The bones of the foot articulate with one another to createjoints. The joints of the foot, through these articulations, allowmovement to occur. The motion capability of a particular joint isdependent upon bony articulations, ligamentous reinforcements andmuscular control. Motion capability of specific joints of the foot hasbeen studied quite extensively through history. These scientific studieshave identified fourteen different axes of rotations of all the jointsof the human foot. They have through thoughtful analysis determined howthese axes of rotations and motion capabilities function in human gaitand running and jumping activities. The prosthetic foot of the presentinvention has been made in light of these scientific studies with a viewtoward providing an improved prosthetic foot that mimics the human footin function in order to provide the amputee with normal human gaitcharacteristics and improve the quality of life of the amputee.

[0007] A prosthetic foot according to the present invention comprises aforefoot portion, a midfoot portion and a hindfoot portion, wherein thehindfoot portion includes first and second joints permitting closedkinetic chain motion of the prosthetic foot in gait. The first joint hasa joint axis oriented for permitting motion of the hindfoot portionabout the first joint axis which is at least primarily in the sagittalplane. The second joint has a joint axis oriented for permitting motionof the hindfoot portion about the second joint axis which is at leastprimarily in the frontal and transverse planes. In the disclosed exampleembodiments, the first and second joints are formed integrally with thehindfoot portion by respective struts of resilient material of thehindfoot portion. More particularly, in one example embodiment theforefoot, midfoot and hindfoot portions of the prosthetic foot areformed of a single piece of plastic as by molding and/or machining.

[0008] In a second embodiment, the improved prosthetic foot of theinvention is formed by use of an ankle pylon component of the inventionwhich is attached to an existing low profile prosthetic foot as afunctional upgrade. The ankle pylon component contains the first andsecond joints which form part of the hindfoot portion of the foot. Inboth embodiments, the first joint in the hindfoot portion mimics anankle joint and the second joint mimics a subtalar joint to allow thefoot to function like a normal foot.

[0009] The subtalar joint in the hindfoot portion of the disclosedembodiments constitutes a means for permitting triplanar closed kineticchain motion of the prosthetic foot in gait. This triplanar motioncapability improves the foot staying plantar grade during the stancephase of gait. It also decreases residual limb to socket shear forcesassociated with motion in the transverse plane.

[0010] These and other objects, features and advantages of the presentinvention will become more apparent from the following detaileddescription of the disclosed, example embodiments, taken with theaccompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

[0011] The foregoing and a better understanding of the present inventionwill become apparent from the following detailed description of theexample embodiments and the claims when read in connection with theaccompanying drawings, all forming a part of the disclosure of thisinvention. While the foregoing and following written and illustrateddisclosure focuses on several example embodiments of the invention, itshould be clearly understood that the same is by way of illustration andexample only and the invention is not limited thereto. The spirit andscope of the present invention are limited only by the terms of theappended claims.

[0012] The following represents brief descriptions of the drawings,wherein:

[0013]FIG. 1 is a perspective view, from the right front and slightlyabove, of a right prosthetic foot according to a first exampleembodiment of the invention.

[0014]FIG. 2 is a lateral side view of the prosthetic foot of FIG. 1located within a cosmetic covering of the foot, shown in dashed lines,and in position for connection with an adjoining prosthesis on theamputee's leg, also shown in dashed lines.

[0015]FIG. 3 is a medial side view of the prosthetic foot of FIG. 1.

[0016]FIG. 4 is a top view of the prosthetic foot of FIG. 1.

[0017]FIG. 5 is a bottom view of the prosthetic foot of FIG. 1.

[0018]FIG. 6 is a schematic view of the ankle joint axis of theprosthetic foot as projected on the frontal plane wherein it is seenthat the ankle joint axis is deviated from the transverse plane by anangle β with the medial more proximal than the lateral.

[0019]FIG. 7 is a cross-sectional view of the ankle joint strut takenalong the section VII-VII in FIG. 3.

[0020]FIG. 8 is a schematic view of the ankle joint axis of theprosthetic foot as projected on the sagittal plane wherein it is seenthat the ankle joint axis is deviated from the transverse plane by anangle θ with the anterior more proximal than the posterior.

[0021]FIG. 9 is a schematic view of the subtalar joint axis of theprosthetic foot as projected on the sagittal plane showing the subtalarjoint axis making an angle ψ with the transverse plane with the anteriormore proximal than the posterior.

[0022]FIG. 10 is a schematic view of the subtalar joint of theprosthetic foot as projected on the frontal plane with the axis makingan angle ω with the transverse plane with the medial more proximal thanthe lateral.

[0023]FIG. 11 is an enlarged top dorsal view of the prosthetic foot ofFIG. 1 wherein shading lines have been added to show the locations ofconcavities and convexities on the dorsal surface of the body of thefoot for effecting motion of the foot in gait.

[0024]FIG. 12 is an enlarged, bottom plantar view of the body of theprosthetic foot of FIG. 1 to which lines have been added to showmid-stance contact areas of the foot on a level surface in gait and towhich shading lines have been added to depict concavities on the plantarsurface of the body for effecting motion of the foot in gait.

[0025]FIG. 13 is a cross-sectional view through a lower portion of themidfoot portion of the body of the prosthetic foot taken along the lineXIII-XIII in FIG. 2 showing the inclination of the longitudinal arch atangle Σ with the transverse plane with the medial more proximal than thelateral.

[0026]FIG. 14 is a side view of an integrally formed metal attachmentdevice for the prosthetic foot.

[0027]FIG. 15 is a top view of the device in FIG. 14.

[0028]FIG. 16 is a top view of the lower attachment plate of the deviceof FIG. 14.

[0029]FIG. 17 is a perspective view of an ankle apparatus of theinvention with a pylon attached at an upper surface thereof, the ankleapparatus being useful as an attachment to an existing low profileSeattle or similar prosthetic foot as a functional upgrade component tothe foot, the combination forming another embodiment of an improvedprosthetic foot according to the invention.

[0030]FIG. 18 is a side view of the right side of the ankle apparatus ofFIG. 17.

[0031]FIG. 19 is a front view of the ankle apparatus of FIG. 17.

[0032]FIG. 20 is a side view of the left side of the ankle apparatus ofFIG. 19.

[0033]FIG. 21 is a rear view of the ankle apparatus of FIG. 17.

[0034]FIG. 22 is a bottom view of the ankle apparatus oriented as shownin FIG. 21.

[0035]FIG. 23 is a rear view of the ankle apparatus similar to FIG. 21but showing in dashed lines a T-shaped nut which is embedded in theresilient body of the ankle apparatus for attaching the ankle apparatusto a prosthetic foot using a threaded bolt.

[0036]FIG. 24 is a top view of the T-shaped nut which appears in dashedlines in FIG. 23.

[0037]FIG. 25 is a side view of the T-shaped nut of FIG. 24 and athreaded bolt received therein.

[0038]FIG. 26 is a top view of a port of a conventional low profileSeattle or similar prosthetic foot sectioned longitudinally along lineXXVII-XXVII.

[0039]FIG. 27 is a side view of the prosthetic foot of FIG. 26.

[0040]FIG. 28 is a side view of the prosthetic foot according to anotherembodiment of the invention.

[0041]FIG. 29 is a perspective from the medial side, above and towardthe front of another embodiment of a left prosthetic foot of theinvention.

[0042]FIG. 30 is a top view of the prosthetic foot of FIG. 29.

[0043]FIG. 31 is a side view of the prosthetic foot of FIGS. 29 and 30from the medial side.

DETAILED DESCRIPTION OF DISCLOSED EMBODIMENTS

[0044] Referring now to the drawings, a prosthetic foot 1 of a firstexample embodiment of the invention comprises a body 2 formed of aresilient, semi-rigid material, plastic in the disclosed embodiment,which is formed with forefoot, midfoot and hindfoot portions 2A, 2B and2C, respectively. A cosmetic covering 3 of the foot surrounds the body 2as depicted in FIG. 2. The body 2 in the disclosed embodiment is formedby molding or by pouring the material of the body into a negative mold.However, other processes could be employed to form the body 2 such asmachining the body from a solid piece of resilient, semi-rigid material,or by using a combination of molding and machining, for example. Theplastic of body 2 is an elastomer, polyurethane in the illustratedexample but other plastics or composite materials could be used. Thebody 2 of the foot is shaped and designed to simulate a human foot'shindfoot triplanar, forefoot biplanar and hindfoot, midfoot and forefootdynamic response windless effect motion capabilities as discussedherein.

[0045] The rear foot triplanar motion capability is achieved by thehindfoot portion 2C which includes first and second joints 4 and 5permitting closed kinetic chain motion of the prosthetic foot in gait.The first joint 4 acts as an ankle joint. The second joint 5 acts as asubtalar joint. The ankle joint axis of rotation 4A is oriented forpermitting motion of the hindfoot portion 2C about the joint axis 4Awhich is at least primarily in the sagittal plane. More particularly,the ankle joint axis 4A is preferably externally rotated an angle α of8° to 30° from a line drawn normal to the long axis X-X of the foot, seeFIG. 4. The ankle joint axis 4A also deviates from the transverse planean angle β of 8° with the medial more proximal than the lateral, seeFIG. 6. This ankle joint axis of rotation orientation allows theprosthetic foot to mimic human foot ankle joint sagittal and frontalplane motion capabilities.

[0046] Motion in the open chain cannot occur in the prosthetic footbecause of the lack of muscular control. However, in closed kineticchain motion, dorsiflexion with abduction appears as forward movement ofthe leg on the foot with internal rotation of the leg. Plantar flexionwith adduction appears as backward movement of the leg on the foot withexternal rotation of the leg. Ground reaction forces create thesemotions by way of the prosthetic foot 1.

[0047] The ankle joint 4 and subtalar joint 5 are formed integrally withthe hindfoot portion 2C by respective struts 4B and 5B of the resilientmaterial of the hindfoot portion. The struts are each elongated in thedirection of their respective joint axis. The anterior and posteriorside surfaces of the ankle joint strut 4B and the medial and lateralside surfaces of the subtalar joint strut 5B are concavely curved fortransferring and absorbing forces in motion of the hindfoot portionabout the ankle and subtalar joint axes. The concavely curved anteriorside surface of the strut 4B is formed by the periphery of a hole 6which extends through the hindfoot portion 2C along the anterior side ofthe strut 4B. The diameter d₁ of hole 6 in foot 1 is ⅝ inch but this canvary dependent upon the overall size of the body 2 of the foot 1.

[0048] Anterior to the hole 6 is a gap 7 which permits the motion of thehindfoot portion 2C about the joint axis 4A. The height 8 of gap 7 isselected so that a lower surface of the body 2 adjacent the gap 7 actsas a stop against an opposing upper surface defining the gap to limitthe amount of motion of the hindfoot portion 2C about the ankle jointaxis 4A in dorsiflexion. The wider the anterior gap, the more potentialfor dorsiflexion range of motion. The hole 6 in the illustratedembodiment extends in a direction parallel to the joint axis 4A.

[0049] The posterior aspect of the ankle joint strut 4B of the hindfootportion 2C is a concavity having a diameter d₂ of 1½-2 inches in theexample embodiment but this can vary and is determined by the overallsize of the body 2. For example, for an infant or small child's foot thediameter d₂ would be smaller. The proximal aspect of concavity 9preferably extends in a direction parallel to the ankle joint axis 4A.The distal aspect of concavity 9 can extend in a direction parallel tothe ankle joint axis 4A or extends in a direction parallel to thefrontal plane. This curvature is necessary to absorb shock and to allowfreer plantarflexion range of motion about the ankle joint. To createankle joint motion capability, the width w and thickness t of theplastic ankle strut 4B, see FIG. 7, can be varied as can the density,durometer and other properties of the material utilized. For example, anabove the knee prosthetic foot needs different motion characteristicsthan a below the knee prosthetic foot.

[0050] It is well understood in the prosthetic profession that a heellever creates flexion torque and that a toe lever creates extensiontorque. As a consequence, the motion requirements are different forabove the knee and below the knee prosthetic feet. As a result, an abovethe knee prosthetic foot may have a different posterior ankle jointconcavity radius of curvature and it may be formed of a less densematerial. This in effect, would decrease the heel lever and theresultant flexion torque associated with it. The ankle joint axis 4A asprojected on a sagittal plane is inclined from the transverse plane anangle θ with the anterior being more proximal than the posterior, seeFIG. 8. The angle θ in the enclosed embodiment is the same as the angleβ in FIG. 6, 8°.

[0051] The subtalar joint 5 in the prosthetic foot 1 is spaced below andextends in a different direction than the ankle joint 4. The subtalarjoint axis 5A extends along the subtalar joint strut 5B and is orientedfor permitting motion of the hindfoot portion 2C about the joint axis 5Ain all three of the frontal, transverse and sagittal planes, althoughprimarily in the frontal and transverse planes. The joint axis 5A runsin the hindfoot portion 2C from posterior, plantar and lateral toanterior, dorsal and medial. Preferably, the joint axis 5A as projectedon a transverse plane is inclined at an angle Δ₁ of 9° to 23° with thelongitudinal axis of the foot, X-X in FIG. 4. The angle Δ₁ is 23° in theexample embodiment. The joint axis 5A as projected on a sagittal plane(the oblique axis of joint 5), as seen in the direction of arrow B inFIG. 1, makes an angle ψ of 29° to 45° with respect to the transverseplane, see FIG. 9. The angle ψ is 30° in the disclosed embodiment.

[0052] The subtalar joint 5 is bounded medially and laterally byrespective holes 10 and 11 which extend parallel to the joint axis 5A.The diameter d₃ of the holes is variable depending on the overall sizeof the body 2. It is {fraction (3/16)} inch in the example embodiment.Medial and lateral gaps 12 and 13 extend along the subtalar jointoutwardly from the holes 10 and 11, respectively, to the periphery ofthe body 2 of the foot to permit the motion of the hindfoot portion 2Cabout the subtalar joint axis 5A. The height 14 of the medial gap 12 andthe height 15 of the lateral gap 13 are selected so that a lower surfaceof the hindfoot portion 2C defining each gap acts as a stop against theopposing upper surface defining the gap to limit the amount of bendingor rotational motion of the hindfoot portion about the joint axis 5A ineversion and inversion in gait. The height of the medial gap 14 ispreferably greater than, such as twice that of the lateral gap 15. Theheight 14 is ⅛ inch and height 15 is {fraction (1/16)} inch in theexample embodiment. The joint axis 5A as projected on the frontal plane,as seen in the direction of arrow A in FIG. 2, is inclined an angle ω tothe transverse plane with the medial being more proximal than thelateral, see FIG. 10.

[0053] The subtalar joint axis of rotation 5A in the prosthetic foot 1mimics the human foot's subtalar joint in function. The significance ofthe longitudinal axis of rotation 5A of the joint 5 being orientedexternally 9-23° from the long axis of the foot is in allowing medialand lateral or frontal plane motion capability. The amount of possiblefrontal plane motion of the prosthetic foot at the joint 5 is dictatedby the height of the medial and lateral subtalar joint gaps 14 and 15.Since the human foot typically has 20° inversion and 10° eversion rangeof motion capability about the human foot subtalar joint, the medial gap14 of prosthetic foot 1 is, as noted above, preferably twice as wide asthe lateral gap 15 to allow a greater range of inversion than eversion.

[0054] The curvature on the medial and lateral sides of the strut 5Bprovided by the holes 10 and 11 prevents the plastic from breaking byreducing stress concentration. The subtalar joint's oblique axis ofrotation, FIG. 9, allows the joint to act as a mitered hinge. A simpletorque converter has been created and rotation of the leg or verticalsegment connected to the foot 1 will result in near equal rotation (inthe case ψ is 45°) of the horizontal segment. This orientation willimprove transverse and frontal plane motion capability. When the angle ψof the oblique axis of the subtalar joint 5 is 30° instead of 45°, theaxis is twice as close to the horizontal plane as to the vertical planeand twice as much motion of the foot occurs in the frontal plane as inthe transverse plane with a given rotation of the leg about itslongitudinal axis. The importance of transverse plane motion capabilityat the subtalar joint 5 is for transverse plane torque absorption, forreduction of shear forces at the residual limb to socket interface andfor avoiding the need to add a separate torque absorber to theprosthetic foot.

[0055] The average transverse plane rotation of the lower leg of aperson in gait is 19°. The subtalar joint is the mechanism in the humanfoot, and also in the prosthetic foot 1, which allows these 19° ofrotation to occur. Closed kinetic chain motion of the subtalar joint 5in the foot 1 remains inversion with supination and eversion withpronation in the frontal plane. The subtalar joint functional range ofmotion in gait is 6° total motion. In the case only 6° of frontal planemotion is needed in the prosthetic foot 1, it is possible to incline theoblique axis of the joint 5 toward the upper end of the range 30°-45° toderive a comfort benefit.

[0056] The hindfoot portion 2C of the foot 1 is also formed with a heel16 with a posterior lateral corner 17 which is more posterior andlateral than the medial corner of the heel to encourage hindfooteversion during the initial contact phase of gait. As shown in FIGS. 4and 5, the posterior aspect of the heel 16 is a duck-tail shaped torsionbar with the lateral posterior corner 17 thereof offset a distance I₁ of½ to ¾ inch more posterior than the medial corner. The use of a smallerangle Δ of 16°, for example, or a more medial positioning of thesubtalar joint strut 5B as discussed later also causes the heel corner17 to be offset a distance of I₂ of ½ inch more lateral than theprojected axis of the subtalar joint. This ½ inch lateral offsetpredisposes the rear foot at heel strike to cause the subtalar joint toevert. This initial contact subtalar joint eversion acts as a shockabsorber to dampen the impact of the heel strike. In addition, the shapeof the posterior lateral corner of the foot in the sagittal plane iscurved upwardly, see FIGS. 2 and 3, with a radius of curvature of 1½ to3 inches in the disclosed embodiment. This radius of the curvature canvary depending on the overall size of the foot. This large radius ofcurvature allows the posterior lateral corner to deflect proximally atheel strike which also acts as a shock absorber. The density of plasticin the posterior aspect of the body 2 of the foot 1 could also beselected to be less than that in the rest of the body of the foot tocreate even more shock absorption capability.

[0057] The top 23 of the hindfoot portion 2C of the prosthetic foot 1 ismade flat and has a metal attachment device 18 embedded into theplastic. The metal device 18 is made of stainless steel in foot 1, butother high strength, light weight metal alloys, such as Ti alloys, couldbe used utilized. The device 18 permits attachment of the prostheticfoot to a prosthetic component 24 secured to a person's limb above thefoot as schematically depicted in FIG. 2. The lower part 19 of theattachment device 18 is embedded into the material of the hindfootportion 2C during molding. Preferably, this lower part 19 has severalholes therethrough to aid in anchoring the device in the moldedelastomer of body 2 at the time of molding. In the disclosed exampleembodiment, the attachment device comprises an upper pyramid attachmentplate 20 connected in spaced relation to a lower attachment plate 19 bya plurality of fasteners 21 as shown in the drawings. Alternatively, theupper and lower attachment plates and connecting elements could beformed integrally as shown in FIG. 14. The attachment device 18 islocated in the hindfoot portion 2C along the longitudinal axis X-X ofthe foot 1 as shown in the drawings.

[0058] The metal attachment device 18′ in FIG. 14 comprises integrallyformed lower attachment plate 19′, upper pyramid attachment plate 20′and connecting struts 21′. The lower plate 19′ is formed with an ⅛ inchproximal offset 41 on the anterior leaf and medial and lateral offsets42 and 43, respectively. Medial and lateral holes 44 and 45 and anteriorand posterior holes 46 and 47 help anchor the device in the plastic body2 during molding. A line C-C through the holes 44 and 45 is 8° to 30°externally rotated from a normal to the sagittal plane X-X with themedial being further anterior than the lateral. The line C-C ispreferably offset posteriorally a distance X′ from the middle or equalorientation D-D so that the holes 44 and 45 fall in the middle of theankle joint axis strut 4B. The posterior offset of holes 44 and 45,together with posterior hole 47 counter the toe lever length. Thesefeatures can also be used on the device 18 where fasteners join separateupper and lower attachment plates 20 and 19.

[0059] The dorsal surface of the midfoot portion 2B anterior to the gap7 is formed with a dorsal concavity 25 which allows the midfoot portion2B and forefoot portion 2A to dorsiflex as weight is transferred to theanterior portions of the prosthetic foot in gait. A metatarsal archconvexity 26 is provided on the dorsal surface of the midfoot portion 2Banterior and medial from the dorsal concavity 25. In addition, thedorsal aspect of the midfoot portion 2B and forefoot portion 2A isformed with a concavity 27 which mimics in function the fifth ray axisof motion of the human foot. See the different shadings in FIG. 11depicting the locations of concavities 25 and 27 and convexity 26 on thedorsal surface of body 2. The concavity 27 has its longitudinal axis Y-Yoriented at an angle Y of 35° to the longitudinal axis X-X of the footwith the medial being more anterior than the lateral to mimic infunction the fifth ray axis of motion in gait as an oblique lower gearaxis of the rotation of the second to fifth metatarsals in the humanfoot. The angle γ could be less than 35°, but is preferably within therange of 15° to 35°.

[0060] The plantar surface of the body 2 of foot 1 has a longitudinalarch 28, see FIG. 12, which, in the vicinity of locations correspondingto the navicular medially and the base of the fourth metatarsallaterally of the human foot, includes a concavity 29 with itslongitudinal axis oriented normal to the axis Z-Z, the first ray axis ofmotion in the human foot to mimic the function thereof, see FIG. 12where the concavity location is shown by shadings added to the drawingof the plantar surface of the body 2 of foot 1. The axis Z-Z in theexample embodiment is at an angle Σ of 45° to the longitudinal axis X-Xof the foot with the medial more posterior than the lateral. The angle Σcould be less than 45°, but is preferably within the range of 30° to45°. Use of angles for γ and Σ at the lower end of the specified rangeswill decrease the difference between the high and low gear principles.The latter may be utilized on high activity level amputees, for example.The plantar surface of the foot 1 in the anterior portion of thelongitudinal arch concavity further includes a generally annularmetatarsal arch concavity or cupping area 30 delineating the posteriorsurface of a forefoot plantar surface contact area which has beenoutlined at 31 as shown in FIG. 12. A hindfoot contact area is outlinedat 31′.

[0061] The longitudinal arch 28 itself is formed with a concavity havinga longitudinal axis A-A, FIG. 12, that as projected on the frontal planeis deviated at an angle Σ of 25° to 42°, see FIG. 13, with the medialhigher than the lateral to create frontal and sagittal plane motioncapabilities as with the midtarsal joints in the human foot. The medialaspect 32 of the longitudinal arch concavity is larger in radius andmore proximal than the lateral aspect 33 of the concavity. The anterioraspect of the longitudinal arch concavity has its longitudinal axis B-Borientated at an angle η of 35° to the longitudinal axis X-X of the footwith the medial being more anterior than the lateral. The middle aspectof the longitudinal arch concavity has its longitudinal axis A-Aorientation normal to the longitudinal axis X-X of the foot.

[0062] The longitudinal arch 28 is provided with this three-dimensionalfan shape for causing specific motion outcomes of the foot in gait. Theanterior longitudinal arch concavity blends with the first ray andmetatarsal arch concavities 29 and 30. This blending of shapes causesthe anterior longitudinal arch concavity to be more anteriorally andmedially oriented for improving the high gear dynamic responsecapability of body 2. The posterior aspect of the longitudinal archconcavity has its longitudinal axis C-C deviated an angle k of 30° tothe frontal plane with the medial side being more posterior than thelateral, see FIG. 12.

[0063] The midfoot portion 2B is formed of a semi-rigid material asnoted above and the longitudinal arch 28 of the resilient body 2 isshaped to create a dynamic response capability of the foot in gait suchthat the medial aspect 32 of the longitudinal arch has a relativelyhigher dynamic response capability than that of the lateral aspect 33 ofthe longitudinal arch. As a result of this and the aforementionedfeatures of the foot 1, biplanar motion potential exists in the midfootportion 2B corresponding to that in the midtarsal region of the humanfoot where motion occurs in the frontal and sagittal planes enabling theforefoot to remain plantar grade while accommodating the positions ofthe rearfoot during gait. The oblique axes of the midfoot portion 2B aresupinated in the propulsive phase of gait. The windless effect of theplantar aponeurosis activated with heel lift aids supination of theseoblique axes during propulsion. Only 4-6° of frontal plane motion ingait is needed to keep the foot plantar grade. The prosthetic foot'sphysical properties, as well as its surface shapes, dictate motionpotential outcomes. The longitudinal arch area of the prosthetic foot 1is shaped specific to achieve superior functional motion outcomes. Thelongitudinal arch deviation from the sagittal plane as discussed aboveenhances the frontal plane motion and dynamic response characteristicsof the foot 1.

[0064] The proximal section of the midfoot portion 2B is made flat toaccept the forces of the anterior ankle joint dorsiflexion stop adjacentgap 7. The midfoot portion 2B is thicker than the forefoot portion 2A.The medial aspect 32 and 26 of the midfoot portion is thicker than thelateral aspect 33 and 27. The bottom of the foot 1 is made toaccommodate ⅜ inch or ¾ inch heel heights. The plantar surface of thebody 2 in the region of the forefoot and midfoot junction has themetatarsal concavity or cup area 30 as noted above. This cup areafunctions to create contact on the outside edges of the cup. This raisedarea 31 runs parallel to the axis of motion, Y-Y in FIG. 11 of the fifthray.

[0065] The forefoot portion 2A of the body 2 has two expansion joints 34and 35 cut into the posterior end of the forefoot. The medial expansionjoint 34 runs longitudinally to just past the posterior point of groundcontact on the plantar surface of the midfoot portion into the cuppedrecessed area 30, where it terminates in an expansion joint hole 36. Thelateral expansion joint 35 runs further posterior into the forefoot thanthe medial expansion joint 34 where it terminates in an expansion jointhole 37. As a result, the two expansion joints function as do the highand lower gears in the human foot. As seen in FIG. 12, a straight lineB-B connecting the two expansion joint holes 36 and 37 is deviated at anangle η of 35° externally from the long axis of the foot. Since thedistance from the ankle joint to the oblique axis B-B is shorter on thelateral side than the medial side, this axis is used first on heel liftbefore the shift to the high-gear function. The function across thehigh-gear or medial side, push-off results in a pronatedforefoot-to-rear foot position and increased weight bearing under themedial forefoot. Thus, the forefoot portion 2A functions to allowbiplanar forefoot motions to occur.

[0066] More specifically, the expansion joints 34 and 35 independentlyallow the forefoot to dorsiflex and invert and plantar flex and evert.This biplanar motion capability keeps the forefoot plantar grade onuneven terrain. The foot 1 mimics the human foot in this regard. As thehindfoot portion 2C changes position, the forefoot and midfoot portionsneed to change positions in the opposite direction. This countertwisting keeps the foot plantar grade.

[0067] The prosthetic foot 1 worn by the amputee acts as a closed chainprosthetic device which responds to the ground forces created in humangait. In the initial contact phase of gait, the posterior lateral heelstrikes the ground. The design of the posterior lateral heel area isoffset as discussed above to transfer weight via the duck tail shapedextension which deflects upwardly to absorb the heel lever forces whichcreate flexion torque of the calf shank. Further enhancement of thistorque absorption and improved shock absorption characteristics of thefoot 1 are provided by the posterior concavity 9 and the lateral offset12 of the heel to the axis of rotation of the subtalar joint 5 such thatwith force application the subtalar joint is made to evert. Thiseversion acts as a shock absorber to dampen the initial contact weighttransfer phase of gait. In addition, force application is posterior tothe axis of rotation 4A of the prosthetic ankle joint 4 causing theankle joint to plantar flex and the midfoot and forefoot portions 2B and2C of the foot to be lowered to the ground.

[0068] With reference to the plantar weight bearing surfaces 31 and 31′of the foot as shown in FIG. 12, as weight is transferred anteriorallyfrom the heel portion to the forefoot portion in the entire stance phaseof gait, ground reaction forces push on the plantar surface of theprosthetic foot 1. As weight is transferred through the hindfoot portion2C, the subtalar joint 5 allows movement in the foot 1 to occur in whatcorresponds to the three cardinal planes of human motion, namely thetransverse, frontal and sagittal planes. This triplanar motioncapability is achieved because of the orientation of the prostheticfoot's subtalar joint axis of rotation 5A which is deviated from thetransverse, frontal and sagittal planes as discussed above. Thisorientation allows motion capability in the three planes. The sagittalplane component is less than that in the frontal and transverse planes.The decreased sagittal plane motion of the subtalar joint 5 iscompensated for by the ankle joint 4 which is located just proximal tothe subtalar joint.

[0069] The subtalar joint's ability to allow motion to occur in thetransverse plane is of significance as in the stance phase of gait, thelower extremity primarily through the subtalar joint must absorb 19° oftransverse plane motion transferred through the tibia and fibula, to theankle joint and then to the subtalar joint. The subtalar joint 5 acts asa mitered hinge and transfers this motion into the hindfoot and midfootportions 2C and 2B. This motion is absorbed in the midfoot dynamicresponse qualities and in the midfoot-forefoot biplanar motioncapabilities. As a result, improved plantar surface weight bearingcharacteristics are achieved. Before foot flat in the stance phase ofgait, as the weight transfer line moves anteriorly in the foot andapproaches the ankle joint 4, the ground reaction forces cause the anklejoint to plantar flex until the entire foot hits the ground. Thisplantar flexion motion is achieved by the ankle joint anterior gap 7spreading or opening further and by the posterior ankle joint concavity9 compressing.

[0070] Once the foot 1 is flat on the ground, the weight is thentransferred into the ankle joint 4. As the weight transfer moves moreanteriorly in the foot, the anterior dorsiflexion gap 7 engages andfurther dorsiflexion motion is arrested. That is, the motion is arrestedby the opposing surfaces defining the anterior ankle joint gap comingtogether. The larger the gap 7, the more dorsiflexion motion potential.The weight transfer to the anterior ankle joint stop adjacent gap 7 isof significance. The weight is thereby transferred into the midfootportion 2B of the foot 1. As a consequence, the area of the longitudinalarch 28 of the foot 1 is loaded and it responds with its concavityexpanding and absorbing these vertical forces. The result is more shockabsorption qualities and dynamic response capabilities.

[0071] The proximal medial longitudinal arch area is much larger inradius than the lateral distal. As a consequence, the medial hasincreased expansion potential and higher dynamic response than thedistal lateral longitudinal concavity of the arch. As the weighttransfer moves even more anterior in the prosthetic foot 1 approachingthe medial aspect of the first ray longitudinal axis of rotation, Z-Z inFIG. 12, the weight transfer is approaching the middle frontal plane ofthe foot.

[0072] The plantar and dorsal surfaces of the prosthetic foot aredesigned to allow or encourage specific motions to occur. Morespecifically, the first ray axis of rotation Z-Z and the motioncapability associated with this axis in the human foot are mimicked inthe prosthetic foot 1 by the plantar surface of the forefoot portion 2Abeing shaped into the concavity 29. The longitudinal axis Z-Z of theconcavity 29 is oriented to be parallel to the longitudinal axis ofrotation of the first ray in the human foot. This orientation is 45°internally rotated to the long axis of the foot, see angle Σ in FIG. 12.

[0073] The motion outcome from force application to this concavity andits degree specific orientation is vertical shock absorption andimproved dynamic response capabilities. The first ray concavity 29, aswell as the longitudinal arch concavity 28 create dynamic responsecapabilities. These dynamic response capabilities are exhibited by theground forces transferring weight to the sides of the concavities andthe concavities expanding. Thus, concavity expansion occurs in theprosthetic foot 1 during gait and once the force is removed, the foot 1springs back into its original shape which releases stored energy.

[0074] The ankle and subtalar joints 4 and 5 in the prosthetic foot 1also have the potential to produce a dynamic response capability. Forexample, as the ankle joint 4 plantar flexes and the anteriordorsiflexion gap 7 spreads and the posterior concavity 9 compresses,energy is stored in the ankle joint strut 4B. The strut 4B will returnto its normal position once the vertical forces are removed.

[0075] Thus, dynamic responses of the prosthetic foot 1 in response toground reaction forces are associated with expansion and compression ofconcavities and convexities and to a lesser degree with movement thatoccurs and the design features of a specific joint's strut. The struts4B and 5B constitute the middle pivot points of class 1 levers in thehindfoot portion 2C. The ankle and subtalar joint struts each haveenergy storing capabilities. The physical properties, as well as thedesign characteristics, create the dynamic response capabilities. Forceapplication will cause movement to occur. Once the force is removed, thephysical properties of the strut make it return to its original restingshape and as a consequence dynamic response has occurred. While theprosthetic foot's first ray axis and fifth ray axis are not distinctjoint axes, the shape and design of the surface features of the body 2of the prosthetic foot dictate functional motion capabilities such thatthese specific motions are encouraged to occur as discussed above.

[0076] The interrelationship between the midfoot's plantar and dorsalshapes are significant in understanding the dynamic responsecapabilities that exist. In this area of the prosthetic foot 1, themedial and lateral surface shapes are shape specific and these shapesprovide functional movement outcomes. In gait, the lateral dorsal fifthray concavity 27 is compressed, allowing less resisted motion potential.This relates to a low gear principle. The medial midfoot plantar anddorsal surface areas as previously described (first ray in function)respond to force application by expanding. Expansion has increasedresistance qualities and as a result dynamic response capabilities areenhanced. This enhanced dynamic response capability is associated with ahigh gear principle.

[0077] The high gear and low gear principles relate to gaitacceleration, deceleration and speed components. The high gear improveddynamic response capabilities can be utilized in gait acceleration anddeceleration phases. A low gear principle relates more to the speed ofgait, rather than the aforementioned acceleration and deceleration. Thelow gear component of the prosthetic foot 1 will allow the amputee toambulate with less energy expenditure while walking at slower speeds.This decrease in energy expenditure is associated with two principles,namely the length of the toe levers as these toe lever lengths relate toextension torque of the calf shank, and to the dynamic responsecharacteristics of the medial and lateral areas of the prosthetic foot.

[0078] The high gear has a longer toe lever than the low gear. When theamputee walks slowly, less momentum and inertia are created. The abilityto efficiently overcome a long toe lever is less. The body's center ofgravity shifts more laterally during slow walking in the stance phase ofgait. With the improved frontal plane motion capabilities of theprosthetic foot 1, the patient's calf shank can be positioned to moveinto the low or high gear sections of the midfoot and forefoot areas. Ifthe amputee wearing the foot 1 is accelerating or decelerating, he willutilize the higher gear function once reaching a comfortable gait speed.The amputee will seek an area of the forefoot 2A which allows thecomfortable gait speed to continue. The force transfer will occur moremedial if the amputee wants more dynamic response characteristics ormore lateral for less dynamic response characteristics. With theprosthetic foot 1, the amputee has a choice of functional movementoutcomes.

[0079] Improved overall amputee gait patterns are the result of suchselective control. As the weight transfer moves even further anteriorlyin the prosthetic foot 1, the axis of the fifth ray is replicated by thearrangement of the two expansion joint holes 36 and 37 and by the shapeand design of the plantar and dorsal surfaces of the body 2 of the foot.That is, the dorsal aspect of the body 2 about the fifth ray's axis ofrotation Y-Y is shaped into a concavity, 27. This concavity encouragesmotion to occur perpendicular to the longitudinal axis orientation Y-Y.It is known that in normal gait the calf shank, tibia and fibula do notprogress solely in the sagittal plane. It is known that at midstance,the knee or calf shank migrates laterally and frontal plane motions alsooccur. This is exhibited in the human knee by the larger surface area ofthe medial femoral condyle.

[0080] The function of the fifth ray axis of rotation Y-Y in foot 1 isimportant. As weight is transferred anterior and laterally to theprosthetic foot 1, the fifth ray longitudinal axis Y-Y allows motion tooccur perpendicular to its longitudinal axis orientation. Additionally,the two expansion joint holes 36 and 37 are positioned to encourageforefoot motions that are positioned on the fifth ray's longitudinalaxis of rotation and, as a consequence, improved biplanar motioncapabilities are created. The low gear and high gear effects referred toabove are also enhanced. As a result, the prosthetic foot gaitcharacteristics are improved and human gait is mimicked.

[0081] The biplanar forefoot qualities of the prosthetic foot 1 areenhanced by the expansion joints and expansion joint holes as referredto above. The two expansion joint holes are strategically placed tocreate specific motion capabilities. That is, the two holeslongitudinally, as projected on the sagittal plane are oriented at angleb of 45° from the line B-B parallel to the frontal plane, see FIG. 2.This orientation acts as a mitered hinge much like the mitered hinge ofthe subtalar joint. Improved biplanar motion capabilities are theresult.

[0082] The plantar surface weight bearing surface 31 of the forefootportion 2A and 31′ of the hindfoot portion 2C are also design and shapespecific. The plantar surface expansion joint holes 36 and 37 arelocated in the metatarsal arch area 30. As a consequence, as weight istransferred onto the area of the foot 1 equivalent to the metatarsalheads, the weight is borne on the expansion joint struts 38, 39 and 40.As the weight-bearing surface on the plantar aspect of the foot 1contacts the ground, weight is borne by the expansion struts, causing asuspended web effect. This allows a tremendous amount of formingability, while maintaining the structural stability needed for a soundstable foot. With the improved biplanar forefoot motion capabilities ofthe prosthetic foot, human gait is improved.

[0083] As the weight transfer in gait moves even further anteriorly intothe region of the expansion joint struts and ray area, the prostheticfoot 1 is shaped and designed to create specific motion outcomes. Thedorsal and plantar aspects of the aforementioned region of the body 2are shaped in an upwardly extending arch, see FIG. 2. The dorsal aspectconcavity is oriented to flow into the fifth ray concavity 27. Thismelding of shapes, one into another, makes for a smooth transitionbetween late stance phase and swing phase of gait. The upwardly shapedray region functions as dorsiflexed toes in the aforementioned gaitsequence.

[0084] Although the prosthetic foot of the invention has been describedin connection with the first example embodiment, alternative embodimentsare possible. For example, there is a spatial relationship of the heightof the ankle joint in the prosthetic foot and how this height effectsthe potential orientation of the oblique axis of the subtalar jointstrut in the foot. In the disclosed embodiment, the height of thehindfoot (plantar surface to pyramid attachment surface) is 3-3½ inches.This height could be made larger and the ankle joint's orientation movedmore proximal. This alternate orientation of the ankle joint allows theoblique axis of the subtalar joint to approach and be changed from29-30°, to an angle of 42-45°, for example. The 30° orientation in thedisclosed embodiment provides increased inversion and eversion (frontalplane motion) and decreased abduction and adduction (transverse planemotion). With the alternate embodiment having an ankle joint that ispositioned more proximal, a 45° oblique subtalar joint axis will allowequal transverse and frontal plane motions. The net effect of thislatter orientation would be to decrease inversion/eversion frontal planemotion and increase abduction and adduction of the foot as compared withthe foot of the example embodiment. This increase in abduction andadduction would be resisted by the ground reaction forces and as aconsequence there would be a decrease in the inversion and eversioncapabilities and an increase in transverse plane motions.

[0085] Another possible variation would be to shift the subtalar jointstrut more medial in the foot 1 and thus increase the lateral offset I₁in FIG. 4. This would predispose the subtalar joint to increasedeversion in the initial contact phase of gait. The net effect would beimproved shock absorption capabilities. Further, the two expansion jointholes sagittal plane orientation could be changed from that in the firstillustrated embodiment. These holes could be deviated medially orlaterally in the frontal plane. The result of a non-sagittal orientationof these two holes is expansion joints and expansion struts which movein a more medial and lateral direction. For example, if the twoexpansion joint holes dorsal ends were deviated laterally 20-30° fromthe sagittal plane, the three expansion joint struts when acted upon bythe ground reaction forces are predisposed to encourage dorsiflexion andadduction. Orienting the dorsal aspect of the expansion joint holesdeviated 20-30° medially from the sagittal plane would encouragedorsiflexion and abduction of the struts. In addition, it is possible toorient the two expansion joint holes so that one hole is deviatedmedially and the other hole is deviated laterally. For example, thelateral expansion joint hole's dorsal aspect could be deviated mediallyfrom the sagittal plane 35°. This orientation will predispose thelateral expansion joint strut to move easier into dorsiflexion andabduction—an improved low gear effect. The medial expansion joint hole'sdorsal aspect could be deviated 45° laterally from the sagittal plane.This orientation would predispose the medial expansion strut to moveinto dorsiflexion and adduction. The net effect is to improve the motioncapability of the medial expansion joint strut as its motion is relatedto the high gear effect.

[0086] A still further alternate embodiment of the prosthetic foot is tohave a single expansion joint and expansion joint hole so that onlymedial and lateral expansion joint struts are formed. This wouldincrease the stiffness of the forefoot and decrease its biplanar motioncapabilities. As previously discussed, this single expansion joint holedesign could be deviated from the sagittal plane as described. Anexpansion joint or joints could also be provided in the heel area of thefoot to improve the plantar surface of the heel staying plantar grade onuneven surfaces. The ankle joint could also be moved below the subtalarjoint in the prosthetic foot. This would allow an increase in theinclination of the subtalar joint without affecting the overall heightof the foot—a benefit in a low profile version of the prosthetic foot.

[0087] The body 2 of the prosthetic foot 1 can also be molded as ahybrid type foot using materials of different densities and durometersin the forefoot and midfoot portions 2A and 2B as well as in thehindfoot portion 2C. The physical properties, as well as the designcharacteristics of the foot create its dynamic response capabilities.

[0088] A prosthetic foot 50 according to a second example embodiment ofthe invention is shown in FIG. 28. The prosthetic foot 50 comprises anankle apparatus, e.g., an ankle pylon component, 51, according to thepresent invention which is attached to a conventional low profileSeattle or similar prosthetic foot 52 to improve the hindfoot functionalcharacteristics of the foot. The ankle pylon component has a T-shapednut 53 (see FIGS. 23-25), embedded in its distal end for attaching thecomponent to the foot keel 54 of the foot 52 by way of a bolt 55. Thebolt extends through a stepped hole 56 in the foot keel and a cosmeticcovering 57 of the foot 52.

[0089] The shape and functional characteristics of the ankle pyloncomponent are like those of the hindfoot 2C of the prosthetic foot 1 ofthe first example embodiment. Once attached to the top of the prostheticfoot, a posterior concavity 58 is formed. An anterior concavity 59 withsmooth flowing lines is also formed as seen in the drawings. The pyloncomponent 51 has triplanar hindfoot motion capability because of theaforementioned features described in connection with the hindfootportion 2C of the prosthetic foot of the first example embodiment. Thesefeatures include the presence of first and second joints 60 and 61 whichact as ankle and subtalar joints, respectively. The T-shaped nut orsimilar fastener is embedded into the mistal surface of the resilientplastic material of the component 51 at the time of manufacturing.

[0090] The prosthetic foot 60 according to the embodiment of theinvention shown in FIGS. 29-31 comprises a forefoot portion, a midfootportion and a hindfoot portion as identified in the earlier describedembodiments, see FIG. 3, portions 2A, 2B and 2C for example. Thehindfoot portion of prosthesis 60 includes an ankle joint 61 permittingclosed kinetic chain motion of the prosthetic foot in gait. The anklejoint has a joint axis 61A oriented for permitting motion of thehindfoot portion about the ankle joint axis which is at least primarilyin the sagittal plane. As in the pervious embodiments, the ankle jointis formed integrally with the hindfoot portion by a strut of resilientmaterial of the hindfoot portion. A hole 62 extends through the hindfootportion with the periphery of the hole forming an anterior side surfaceof the strut. The hindfoot portion anterior to the hole includes a gap63 to permit the motion of the hindfoot portion about the ankle jointaxis. The hole 62 as seen in a cross section of the prosthetic foot inthe sagittal plane is elongated upwardly such that the strut isupstanding and anterior facing convexly curved, see FIG. 31.

[0091] The strut extends in the direction of the ankle joint axis 61Aand has an anterior side surface 64 and a posterior side surface 65which are anterior facing convexly curved. As in the previouslydescribed embodiments, the height of the gap 63 is selected so that alower surface defining the gap acts as a stop against on opposing uppersurface defining the gap to limit the amount of motion of the hindfootportion about the ankle joint axis in dorsiflexion. The hole 62 extendsin a direction parallel to the ankle joint axis. The anterior convexlycurved strut advantageously provides differential properties incompression and expansion of the strut in gait and, together with theupwardly arched resilient foot of the prosthesis contributes to adynamic response of the prosthesis having horizontal and verticaldirectional components for improved efficiency of the prosthesis in use.

[0092] The prosthetic foot 60 has a known, commercially availableadapter 66 connected to the resilient, monolithically formed body of theprosthesis forming the foot and ankle by a threaded fastener 67. Theadapter includes a member 68 containing a socket 69 for receiving amember, not shown, to detachably connect the prosthetic foot to anamputee's leg stump. A base 70 of the adapter is located beneath themember 68. When the threaded fastener 67, the top of which has an Allensocket 71 therein for receiving an Allen wrench to permit loosening themember on the base, is untightened, the member can be rotated relativeto the base and prosthetic foot. This relative rotation is in thetransverse plane and allows for easy toeing in and out of the foot towithin critical limits, e.g. to within ⅛ inch.

[0093] The socket 69 of the member 68 is a square socket, with roundedcorners, for receiving with clearance a square complementarily shapedprojection/member on the lower extremity socket or other component onthe amputee's leg stump. See the dashed lines in FIG. 31. Four screws,not numbered, one in the middle of each side wall of the square socketcan be screwed into and out of engagement with the projection forconnecting the prosthesis to the supporting structure on the amputee'sleg stump. The clearance between the projection and the socket and theadjustability of the positions of the four screws of the adapter permitanterior-posterior, medial-lateral, and angular or tilt adjustment ofthe prosthesis and supporting structure. Instead of the adapter 66, theprosthesis 60 could be provided with another known, commerciallyavailable adapter, such as a pyramid type adapter as shown in FIGS. 1-3,for example.

[0094] This concludes the description of the example embodiment andpossible variations or alternative embodiments. However, it should beunderstood that numerous other modifications and embodiments can bedevised by those skilled in the art that will fall within the spirit andscope of the principles of this invention. More particularly, reasonablevariations and modifications are possible in the component parts and/orarrangements of the subject combination arrangement within the scope ofthe foregoing disclosure, the drawings, and the appended claims withoutdeparting from the spirit of the invention.

We claim:
 1. A prosthetic foot comprising a forefoot portion, a midfootportion and a hindfoot portion, said hindfoot portion including an anklejoint permitting closed kinetic chain motion of the prosthetic foot ingait, said ankle joint having a joint axis oriented for permittingmotion of said hindfoot portion about said ankle joint axis which is atleast primarily in the sagittal plane, said ankle joint being formedintegrally with said hindfoot portion by a strut of resilient materialof said hindfoot portion, wherein a hole extends through said hindfootportion with the periphery of the hole forming an anterior side surfaceof said strut, wherein the hindfoot portion anterior to said holeincludes a gap to permit said motion of said hindfoot portion about saidankle joint axis, and wherein said hole as seen in a cross section ofthe prosthetic foot in the sagittal plane is elongated upwardly suchthat said strut is upstanding.
 2. The prosthetic foot according to claim1, wherein said strut extends in the direction of the ankle joint axis.3. The prosthetic foot according to claim 1, wherein the anterior sidesurface and a posterior side surface of said strut are anterior facingconvexly curved.
 4. The prosthetic foot according to claim 1, whereinthe height of said gap is selected so that a lower surface of saidhindfoot portion defining said gap acts as a stop against an opposingupper surface defining said gap to limit the amount of said motion ofsaid hindfoot portion about said ankle joint axis in dorsiflexion. 5.The prosthetic foot according to claim 1, wherein said hole extends in adirection parallel to said joint axis of said ankle joint.
 6. Theprosthetic foot according to claim 1, further comprising an adapterconnected to the prosthetic foot above the ankle joint, the adapterhaving a socket for receiving a member to detachably connect theprosthetic foot to an amputee's leg stump.
 7. The prosthetic footaccording to claim 6, wherein said adapter includes a member containingsaid socket, a base underlying said member and a releasable fastenerconnecting said member on said base to permit relative rotation of themember and the base.
 8. The prosthetic foot according to claim 7,wherein said relative rotation of the socket containing member on thebase of the adapter is in the transverse plane.
 9. The prosthetic footaccording to claim 6, wherein said adapter includes a plurality ofadjustable fasteners for changing the position said member is receivedin said socket.
 10. The prosthetic foot according to claim 9, whereinsaid adapter with socket and adjustable fasteners permitanterior-posterior, medial-lateral and tilt adjustments of the memberand prosthetic foot.
 11. A prosthesis comprising: a foot; an ankle;wherein the foot and ankle are monolithically formed as a resilientmember including a strut which forms an ankle joint permitting closedkinetic chain motion of the prosthesis in gait about an ankle joint axisoriented such that said motion is at least primarily in the sagittalplane, wherein a hole extends through said resilient member with theperiphery of the hole forming an anterior side surface of said strut,wherein said resilient member anterior to said hole includes a gap topermit said motion about said ankle joint axis, and wherein the anteriorside surface of said strut is anterior convexly curved.
 12. Theprosthesis according to claim 11, wherein a posterior side surface ofsaid strut is anterior convexly curved.
 13. The prosthesis according toclaim 11, wherein said hole as seen in a cross section of the resilientmember in the sagittal plane is elongated upwardly such that said strutis upstanding.
 14. The prosthesis according to claim 11, wherein saidstrut extends in the direction of the ankle joint axis.
 15. Theprosthesis according to claim 11, wherein anterior and posterior sidesof said strut and anterior facing convexly curved.
 16. The prosthesisaccording to claim 11, wherein the height of said gap is selected sothat a lower surface of said member defining said gap acts as a stopagainst an opposing upper surface defining said gap to limit the amountof said motion about said ankle joint axis in dorsiflexion.
 17. Theprosthesis according to claim 11, wherein said hole extends in adirection parallel to said joint axis of said ankle joint.
 18. Theprosthesis according to claim 11, further comprising an adapterconnected to the prosthesis above the ankle joint, the adapter having asocket for receiving a member to detachably connect the prosthesis to anamputee's leg stump.
 19. The prosthesis according to claim 18, whereinsaid adapter includes a member containing said socket, a base underlyingsaid member, and a releasable fastener connecting said member on saidbase to permit relative rotation of the member and the base.
 20. Theprosthesis according to claim 19, wherein said relative rotation of thesocket containing member on the base of the adapter is in the transverseplane.
 21. The prosthesis according to claim 18, wherein said adapterincludes a plurality of adjustable fasteners for changing the positionsaid member is received in said socket.
 22. The prosthesis according toclaim 21, wherein said adapter with socket and adjustable fastenerspermit anterior-posterior, medial-lateral, and tilt adjustments of themember and prosthesis.
 23. A prosthetic foot comprising a forefootportion, a midfoot portion and a hindfoot portion, said hindfoot portionincluding an ankle joint permitting closed kinetic chain motion of theprosthetic foot in gait, said ankle joint having a joint axis orientedfor permitting motion of said hindfoot portion about said ankle jointaxis which is at least primarily in the sagittal plane, said ankle jointbeing formed integrally with said hindfoot portion by a strut ofresilient material of said hindfoot portion, wherein a hole extendsthrough said hindfoot portion with the periphery of the hole forming ananterior side surface of said strut, wherein the hindfoot portionanterior to said hole includes a gap to permit said motion of saidhindfoot portion about said ankle joint axis, and wherein said hole isconfigured such that the anterior side surface of said strut is anteriorconvexly curved.
 24. A prosthesis comprising: a foot; an ankle; whereinthe foot and ankle are monolithically formed as a resilient memberincluding a strut which forms an ankle joint permitting closed kineticchain motion of the prosthesis in gait about an ankle joint axisoriented such that said motion is at least primarily in the sagittalplane, wherein a hole extends through said resilient member with theperiphery of the hole forming an anterior side surface of said strut,wherein said resilient member anterior to said hole includes a gap topermit said motion about said ankle joint axis, and wherein said hole iselongated upwardly such that said strut is upstanding.